1. Field of the Invention
This invention relates to an on-line/off-line scoring bridge, and more particularly, to an on-line slit scoring bridge having one or more carriages each having a scoring wheel assembly having a load applying arrangement that applies a constant load to a scoring wheel, and a system to accurately position the carriages on the bridge to reduce spacing error between adjacent carriages on the bridge.
2. Discussion of the Available Technology
On-line slit scoring bridges are used in the glass industry to impose a score or score line in the surface of a glass ribbon parallel to its path of travel as the ribbon moves past a predetermined position downstream of the exit end of the glass annealing lehr. On-line cross scoring bridges are also used to impose a score in the surface of the ribbon transverse to its path of travel. Thereafter the scores are opened to provide glass sheets of a predetermined size. The on-line slit scoring bridges usually have a plurality of spaced carriages each having a scoring wheel set in a predetermined spaced relationship to one another.
Off-line scoring bridges are mounted over a table and usually include a bridge or a carriage having a scoring wheel moveable in the X direction, and the carriage having the scoring wheel or the bridge, respectively moveable in the y direction.
For a more detailed discussion of on-line/off-line scoring bridges, reference can be made to U.S. Pat. Nos. 3,797,339; 4,012,974; 4,204,445 and 5,791,971. The disclosure of the patents is hereby incorporated by reference.
Although the presently available scoring bridges are acceptable, they have limitations. More particularly, the automatic positioning systems and techniques for spacing the carriages relative to one another do not meet current specified tolerances. For example using the presently available technology, an acceptable tolerance between adjacent spaced score lines imposed in the glass ribbon and sheet is ±0.025 inch (0.64 millimeter (“mm”)). As can be appreciated by those skilled in the art, the smaller the difference between the actual dimensions of the cut glass sheet and the desired dimensions of the glass sheet to be used, the less seaming and/or grinding of the glass that is required. Further as can be appreciated by those skilled in the art, reducing the amount of glass that has to be removed, reduces the cost of the glass sheet to be used.
In addition to reducing the tolerance range between adjacent scores imposed in the glass ribbon and sheet, it is appreciated by those skilled in the art that a uniform load should be applied to the scoring wheel to provide scores of uniform depth for ease of opening the scores, and to reduce surface damage to the glass. Variations in load applied to the scoring wheel can result from contours of the glass surface, eccentric conveyor rolls, and/or variations in glass thickness, which raise and lower the scoring wheel, resulting in increased and reduced loads, respectively, on the scoring wheel.
U.S. Pat. No. 4,204,445 discloses a scoring device having a scoring head assembly and a carriage each pivotally mounted about an axis. The carriage has a pair of spaced wheels biased toward a glass ribbon and a support member. The support member biases a scoring force against the scoring head assembly to score the glass ribbon. Irregularities in the glass ribbon thickness and/or eccentric conveyor rolls oscillate the carriage and scoring head assembly about the axis. Oscillatory movement of the carriage and scoring head assembly cooperate to maintain a constant scoring force on the scoring head assembly. Although the scoring device of U.S. Pat. No. 4,204,445 is acceptable, there are limitations. In particular, the scoring device has a large number of moving parts, which makes the scoring device of the patent expensive to construct and maintain.
For additional discussions of glass scoring devices, reference can be made to U.S. Pat. Nos. 3,756,104; 3,760,997 and 4,027,562.
As is appreciated by those skilled in the art, it would be advantages to provide an on-line/off-line scoring bridge that has a system to accurately determine the position of and/or to accurately position the carriages on the bridge to reduce the spacing error between scoring wheels of adjacent carriages on the bridge thereby reducing the tolerance range between adjacent score lines imposed on the glass ribbon by the scoring wheels. It would also be advantageous to provide a load applying device that has a minimum number of moving parts and maintains a constant scoring force on the scoring wheel as the scoring wheel reciprocates along a path toward and away from the surface of the glass ribbon or glass sheet to be scored.